This article will help you quickly take a Raspberry Pi and configure it as an Internet Router.

We focus on OpenWrt 19.07.7 software and Thales IoT 5G, 4G, and 3G Cellular module hardware MV31-W.
Note that only the newest Raspberry Pi 4 and above will offer true multi-100Mb/s throughput.

Internet connectivity is achieved using the high-performance Mobile Broadband Interface Model (MBIM) method.
Note that MBIM doesn't offer DHCP, hence IP config scripts are provided.
 

See related articles:

https://developer.gemalto.com/tutorial/data-transfer-methods
https://developer.gemalto.com/showcase/openwrt-raspberry-pi-networking-pppd
https://developer.gemalto.com/showcase/openwrt-raspberry-pi-networking-wwan
https://developer.gemalto.com/showcase/openwrt-raspberry-pi-networking-qmi
https://developer.gemalto.com/showcase/creating-and-testing-linux-distri...